Solid oxide fuel cell systems include solid oxide fuel cells (SOFCs) configured to react a fuel gas and an oxidant on opposite sides of an electrolyte to generate DC electric current. SOFCs have an anode, an electrolyte and a cathode, and can be made from a variety of materials and in a variety of geometries. The solid oxide fuel cell systems can convert hydrocarbon fuels to a suitable fuel gas containing carbon monoxide (CO) and hydrogen (H2), wherein carbon monoxide and hydrogen gas are then oxidized at an active area of the SOFC to carbon dioxide and water, to generate DC current. Non hydrocarbon fuels such as ammonia (NH3) can also be converted to SOFC fuel using one or more catalytic reactions.
Fuel gas within the solid oxide fuel cell systems is routed to an anode chamber, where the fuel gas reacts with the anode of the SOFC. The operating temperatures of the SOFC is in the range of about 600-950° C. The anode chamber contains low levels of oxygen and therefore, combustion of the fuel gas does not occur to a great extent within the anode chamber. Exhaust gas that includes products of the anode reaction along with unreacted fuel exit the anode chamber through an exhaust outlet. When the exhaust gas exits the exhaust outlet, the unreacted fuel interacts with oxygen present outside the anode chamber, resulting in a combustion reaction. The region at which this combustion reaction takes place is referred to as a flame tip region. The flame tip region comprises an environment with a variable oxidation potential (reducing to oxidative) that is significantly higher than the temperatures present at the anode surface and the cathode surface of the fuel cell, i.e., above the range of about 600-950° C.
The high temperatures of the flame tip region can have an undesirable affect on materials exposed to the high temperatures. For example, fuel cell system components utilized to electrically connect electrodes of individual component cells within a fuel cell stack may comprise materials such as silver or silver alloys, which melt at the temperatures in the range of the temperatures present proximate to the flame tip region. Further, metallic solid oxide fuel cell anodes exposed to the high temperature oxidative environment of the flame tip region will oxidize resulting in irreversible degradation to the fuel cell anode material.
Therefore, it is desirable to control the location of the flame tip region within a fuel cell system.